Question

After reading the definition of aleatory and epistemic uncertainties, make a list of four uncertainties that you had to deal with that you would classify as primarily aleatory. Then do the same thing for four that are epistemic. At least some of these should be related to professional issues:

Aleatory:

1.

2.

3.

4.

Epistemic

1.

2.

3.

4.

Answer 1

*Aleatory uncertainty is generally quantified by a probability or frequency distribution when sufficient information is available to estimate the distribution. We define epistemicuncertainty as a potential inaccuracy in any phase or activity of the modeling process that is due to lack of knowledge.

*Aleatory variability and epistemic uncertainty are terms used in seismic hazard analysis that are not commonly used in other fields, but the concepts are well known.
*Aleatory variability is the natural randomness in a process. *For discrete variables, the randomness is parameterized by the probability of each possible value. For continuous
variables, the randomness is parameterized by the probability density function.
*Epistemic uncertainty is the scientific uncertainty in the model of the process. It is due to limited data and knowledge. *The epistemic uncertainty is characterized by alternative
models. For discrete random variables, the epistemic *uncertainty is modelled by alternative probability distributions. For continuous random variabiles, the epstemic
uncertainty is modelled by alternative probability density functions. In addition, there is epistemic uncertainty in parameters that are not random by have only a single correct (but unknown) value.
*The terms randomness and uncertainty have also been used for aleatory variability and epistemic uncertainty, respectively; however, these terms are commonly used in generic
ways. As a result, they are often mixed up when used in hazard analysis. The terms “aleatory variability” and “epistemic uncertainty” do not roll off the tongue easily. This
unfamiliarity causes people to stop and think about what they are trying to say before using them. The overall goal is to have a clear terminology that will avoid misunderstandings.